The histological structure of the calcified lung of the fossil coelacanth Axelrodichthys araripensis (Actinistia: Mawsoniidae)

Abstract: The palaeohistological study of the calcified internal organ of Axelrodichthys araripensis Maisey, 1986, a coelacanthiform from the Lower Cretaceous of Brazil (Crato (Aptian) and Santana (Albian) formations of the Araripe Basin), shows that the walls of this organ consist of osseous blades of variable thickness separated from each other by the matrix. This indicates that, in the living individuals, the walls were reinforced by ossified plates, probably separated by conjunctive tissue. This calcified sheath present in Axelrodichthys, as well as in other fossil coelacanths, lies in ventral position relative to the gut and its single anterior opening is located under the opercle, suggesting a direct connection with the pharynx or the oesophagus. The calcified organ of Axelrodichthys, like that of other fossil coelacanths, is here regarded as an ‘ossified lung’ and compared with the ‘fatty lung’ of the extant coelacanth Latimeria. The reinforcement of the pulmonary walls by the overlying osseous blades could be interpreted as a means of adapting volumetric changes in the manner of bellows, a necessary function for ventilation in pulmonary respiration. Other functional hypotheses such as hydrostatic and/or acoustic functions are also discussed.     

Palaeoctopus pelagicus from the Turonian of Mexico reinterpreted as a coelacanth (Sarcopterygian) gular plate

Abstract: The supposed vestige of a cephalopod gladius from Turonian platy limestones at Vallecillo, north‐east Mexico, named Palaeoctopus pelagicus by Fuchs et al. in 2008, is reinterpreted and shown to be a gular plate of a coelacanth fish, possibly of the genus Megacoelacanthus. In addition to the gular plate, two extrascapulars and fin rays of all fins are preserved on one slab and its counterpart. This is the first record of a coelacanth from these lower Turonian strata at Vallecillo, which are rich in fish.     

BIOACOUSTIC PUBLICATIONS, 1986

ABSTRACT

A common task for researchers of animal vocalisations is statistically comparing repertoires, or sets of vocalisations. We evaluated five methods of comparing repertoires of ‘codas’, short repeated patterns of clicks, recorded from sperm whale (Physeter macrocephalus) groups. Three of the methods involved classification of codas—human observer classification, k-means cluster analysis using Calinski and Harabasz's (1974) criterion to determine k, and a divisive k-means clustering procedure using Duda and Hart's (1973) criterion to determine k. Two other methods used multivariate distances to calculate similarity measures between coda repertoires. When used on a sample coda dataset, observer classification failed to produce consistent results. Calinski and Harabasz's criterion did not provide a clear signal for determining the number of coda classes (k). Divisive clustering using Duda and Hart's criterion performed satisfactorily and, encouragingly, gave similar results to the multivariate similarity measures when used on our data. However, the relative performance of the k-means techniques is likely data dependent, so one method is not likely to perform best in all circumstances. Thus results should be checked to ensure they extract logical clusters. Using these techniques concurrently with multivariate measures allows the drawing of relatively robust conclusions about repertoire similarity while minimising uncertainties due to questionable validity of classifications.     

云南野生稻叶茎根组织结构特性的比较研究

采用徒手切片法对云南3种野生稻和栽培稻的叶片、茎秆及根的组织结构进行比较研究,以明确野生稻的内部结构,为进一步揭示其结构与云南野生稻的生长势旺盛、营养吸收能力强、抗某些病虫害能力强的关系奠定基础。结果表明,(1)云南野生稻与栽培稻叶片主脉、茎秆及根的组织结构差异显著,其中景洪疣粒野生稻、景洪药用野生稻与栽培稻的差异最明显。(2)在叶主脉结构中,景洪疣粒野生稻无气腔结构,维管束数量少、面积小;景洪药用野生稻、3个普通野生稻材料存在多个维管束和气腔结构,维管束、束内导管直径及气腔面积较栽培稻大,而栽培稻中的气腔均为2个。(3)在茎秆结构方面,景洪疣粒野生稻茎秆最小,维管束数量最少,其茎壁内的维管束排列方式与栽培稻不同;景洪药用野生稻和普通野生稻茎秆及茎壁较栽培稻粗厚,维管束数量也较栽培稻多,普通野生稻的茎壁中有通气组织。(4)在根的组织结构中,3种野生稻的导管数量较多,导管直径及中柱面积较栽培稻大,外皮层出现了具有凯氏带功能的凯氏点等。     

Learning, working memory, and intelligence revisited

Based on early findings showing low correlations between intelligence test scores and learning on laboratory tasks, psychologists typically have dismissed the role of learning in intelligence and emphasized the role of working memory instead. In 2006, however, B.A. Williams developed a verbal learning task inspired by three-term reinforcement contingencies and reported unexpectedly high correlations between this task and Raven's Advanced Progressive Matrices (RAPM) scores [Williams, B.A., Pearlberg, S.L., 2006. Learning of three-term contingencies correlates with Raven scores, but not with measures of cognitive processing. Intelligence 34, 177-191]. The present study replicated this finding: Performance on the three-term learning task explained almost 25% of the variance in RAPM scores. Adding complex verbal working memory span, measured using the operation span task, did not improve prediction. Notably, this was not due to a lack of correlation between complex working memory span and RAPM scores. Rather, it occurred because most of the variance captured by the complex working memory span was already accounted for by the three-term learning task. Taken together with the findings of Williams and Pearlberg, the present results make a strong case for the role of learning in performance on intelligence tests.     

Hedging one's evolutionary bets, revisited

Evolutionary bet-hedging involves a trade-off between the mean and variance of fitness, such that phenotypes with reduced mean fitness may be at a selective advantage under certain conditions. The theory of bet-hedging was first formulated in the 1970s, and recent empirical studies suggest that the process may operate in a wide range of plant and animal species.